Setting the depth of cut on a table saw can become very frustrating when attempting to make accurate cuts.
For many years I used a square to find the height of the blade. This works well for cutting through material completely, but this method has proven to give horrible results when making joints, tenons or rabbit cuts.
Adding a depth gauge to your table saw tools will enable you to quickly get insanely accurate cuts with ease!
Step 1: DESIGN
The core of any great build is to get the details worked out before you waste time or money. Although I grew up in a world of hand drawn paper blueprints, I have found that creating the design in a 3D environment can bring a new world of accuracy and conception that I have not been able to master with a pencil.
You can use any 3D modeling program to create the plans with, but my personal favorite is Fusion 360. Using Fusion you can model any component per spec. You can also test your design and transcribe it into a blueprint/drawing.
Finally, a sweet trick is the capability to print a 1:1 configuration, and thus use this print as a template. I will utilize this trick in this instructable. In this step you can preview some screen shots of the design and the drawings and templates are posted for you to use.
This gauge uses dial calipers. There are several different brands and styles of calipers that range in sizes and lengths. You can adjust the drawings and 3D documents to fit your specific calipers.
Step 2: CONSUMABLES
The concept of this gauge is not new, but is extremely useful and simple to build and use. The materials required are:
.25" (1/4") Plywood
- I used fir for its strength and rigidity (also expense). You could utilize different kinds of stock, i.e., plastic or metal.
.75" (3/4") Wood Screws
- If you have the capability, you could use machine screws as well. For simplicity I used wood screws.
- Wood glue for plywood, for other stock you can choose whatever suits the situation.
-I implanted 2X 1" (0.98) round ceramic disk magnets into the inner slot to give the gauge some grip power so that you can move the dial caliper head up and down with ease. These are not absolutely necessary, but they add a metric ton of usability/stability to the gauge. You can pick these style of magnets up at any hardware store.
Step 3: INITIAL LAYOUT
The layout of the stock is vital to ensure that the gauge will meet tolerance. When you layout a cut pattern on the plywood, mark the factory cut edge so that you will know where the straightest edge is at all times.
Cut 3x rectangles to an oversize of the drawing dimensions (5"X 6").
Cut out the template sheet to the same dimensions. Using a very light coat of wood glue, adhere the "face" template sheet to the face of one of the rectangles. This peice will now be called the face piece.
Using a punch (or a nail) transfer punch through the centerlines of the fastener locations from the face template.
With the face peice on top, stack the other rectangle peices underneath and straighten them against the table saw so that the end grain will seat flush against the flat surface. Clamp the pieces together and re-check the stack for flush.
Step 4: INDEXING AND DRILLING
Using a 3/32 drill bit, drill the fastener locations that were marked earlier. These are through holes that will align and fasten the stack of stock together.
These index holes need to be countersunk to allow the wood screws to seat under torque without splitting the face piece. Use a countersink bit or counter bore drill bit to remove the necessary material.
- (If you are using plastic or metal stock you can utilize machine screws and will not need a countersink or counter bore. Use a drill and tap to resize and thread the index holes to final size.)
Step 5: FASTEN AND SHAPE
Install wood screws in the index holes but do not tighten to final torque. The idea is to use the fasteners as a method of clamping the stock together.
Using a band saw or jig saw, follow the template and remove the excess material outside the template guides. Use sandpaper/orbital sander or a drum sander to bring the final pass to the template line.
Step 6: DISSASEMBLE AND MAKE SLOT CUT-OUTS
At this point the body of the gauge is complete but we need to make the cut-out to provide a slot to hold the dial calipers. Mark the end grain of each piece of stock to enable zero misalignment when reassembled. Use 1, 2, 3, or other code that you can understand.
Disassemble the stock and separate the middle piece. This piece will be cut and become two sides. Cut-out the middle piece template and using wood glue lightly adhere the paper to the middle pieces face. Follow the guidelines of the template and remove the marked material.
Align the sides with the index holes of the back piece and check the fit of your calipers in the slot. Make any additional adjustments/remove additional material to the slot to make the calipers fit without interference.
Step 7: IMBED STABILITY MAGNETS
This step is optional, but really makes this gauge super-powered.
Assemble the face and middle pieces with the wood screws, carefully chasing the original threads. Mark the inside of the face piece using the center pieces as a guide.
Remove the screws and middle pieces and layout two of the disk magnets side by side centered on the bottom of the new marked area.
Now mark (trace) their location onto the inside of the face. Find the center of the marked circles.
Drill a 1/8" hole through the center marks. Use a forsner bit to create a 1" bore. The magnets used in this instructable are .16" thick. To allow for glue and expansion, we will remove .17" material. Be extremely careful when boring to this depth in such thin (.25") material, if available use a drill press with a stop.
Check the magnet fit and ensure that it rests just below the surface. Super-glue the magnets into there new mount holes.
I used a piece of thin plastic (clear packaging material) as a buffer between the magnet and the dial caliper. This plastic can be sandwiched between the middle pieces and face piece during final assembly.
Step 8: RE-ASSEMBLE
Carefully remove/sand off the template paper from the face/middle pieces. At this point it's also recommended that you sand any trouble spots, typically around the through holes.
Realign the pieces (1, 2, 3) and clamp them tightly. Ensure that the edges and the indexing holes are correctly lined up and re-thread the wood screws, this time tighten them to a final torque. During this process be cognizant of how the faces are mating, make sure that they are seated flush without gaps.
Re-check the fit of the calipers into the slot and the how flush the feet seat against the table saw.
Step 9: FINISH/CONCLUSION
At this point your gauge should be ready to put in use. Set the gauge legs on the deck of your table saw and move the caliper head down until the depth gauge contacts the surface. Zero out the calipers (most calipers have this function, but if not you will need to calculate the depth.) Raise the table saw blade and use the legs of the gauge to straddle the blade evenly. Lower the dial calipers depth gauge to make contact with tip of the blade (top dead center tooth). The dial should now display the exact depth of cut! Making tiny adjustments to the blade height I was able to dial in an exact 1" height.
To protect your new gauge, you can coat it anyway you need, just take care to not fill the slot and inadvertently block the caliper from smoothly entering its slot.
Thanks for your time, I hope this instructable helps a maker out there!